AlGaN Barrier Thickness Dependence of Ferroelectric Switching and Interface-Trap Effects in AlScN/HfO2 Gate Stack HEMTs

We investigate the effect of AlGaN barrier thickness (23, 15, and 7 nm) on the transport and switching characteristics of AlScN/HfO2/AlGaN/GaN ferroelectric high-electron-mobility transistors (FeHEMTs). While the 7 nm device exhibits the largest apparent memory window (MW) under quasi-static DC conditions, it suffers from degraded transport, increased leakage, and pronounced trap-induced effects. Pulsed measurements, which reduce the contribution of slower interface-trapping processes, yield representative MWs of 1.6, 3.4, and 2.8 V for the 23, 15, and 7 nm devices, respectively, under their respective program/erase conditions. Prolonged pulse-width measurements demonstrate MW closure and inversion, indicating dominant electron trapping rather than polarization fatigue. Under the present experimental conditions, including a fixed 70 nm AlScN layer, the 15 nm barrier provides the most favorable balance among electrostatic coupling, channel transport, and trap-related effects.